Turbogenerator power control system

ABSTRACT

A power control system for a turbogenerator which provides electrical power to one or more pump-jack oil wells. When the induction motor of a pump-jack oil well is powered by three-phase utility power, the speed of the pump-jack shaft varies only slighty over the pumping cycle but the utility power requirements can vary by four times the average pumping power. This power variation makes it impractical to power a pump-jack oil well with a stand-alone turbogenerator controlled by a conventional power control system. This power control system comprises a turbogenerator inverter, a load inverter, and a central process unit which controls the frequency and voltage/current of each inverter. Throughout the oil well&#39;s pumping cycle, the central processing unit increases or decreases the frequency of the load inverter in order to axially accelerate and decelerate the masses of the down hole steel pump rods and oil, and to rotationally accelerate and decelerate the masses of the motor rotors and counter balance weights. This allows kinetic energy to be alternately stored in and extracted from the moving masses of the oil well and allows the oil pumping power to be precisely controlled throughout the pumping cycle, resulting in a constant turbogenerator power requirement.

TECHNICAL FIELD

[0001] This invention relates to the general field of turbogeneratorcontrols and more particularly to an improved high speed turbogeneratorcontrol system having variable frequency output power which provideselectrical power to motors which have power requirements that normallyvary in a repetitive manner over time.

BACKGROUND OF THE INVENTION

[0002] There are many industrial and commercial applications thatutilize electrical motors to produce repetitive axial motions. Theelectrical motor's rotary motion can be converted into axial motion byany number of mechanisms such as cams, cranks, scotch yokes, or cabledrums just to name a few. In any such application, the electrical powerrequirement of the motor is inherently variable and is cyclically lockedto the repetitive axial motion. The motor power in these applicationsvaries both due to inertial effects (the need to accelerate anddecelerate the axially moving components of the system and the need toaccelerate and decelerate the rotationally moving components of thesystem) and due to the work effects (changes in the work performed bythe axially moving components as a function of their axial position andvelocity). The magnitude of the motor power variation with time can bemany times the average power requirement of the motor. Both the inertialeffects and the work effects can cause the motor to function as agenerator which produces electrical power at various times in thesystem's cyclical motion.

[0003] An elevator is one well-known example of an electrical motorproducing axial motion wherein the motor's electrical power requirementsvary with the passenger load, the axial velocity of the elevator and theaxial acceleration/deceleration of the elevator. Deliberate decelerationor braking can be achieved by recovering the excess energy in theelevator's mechanical system (e.g. during the descent of a heavilyloaded elevator) utilizing regeneration to convert that mechanicalenergy into electrical energy which can go back into an electricaldistribution system.

[0004] A less well known example of a motor producing repetitive axialmotion is a pump-jack type oil well. Also known as a walking beam (alarge beam arranged in teeter totter fashion) or a walking-horse oilwell, the pump-jack oil well generally comprises a walking beam suitablyjournaled and supported in an overhanging relationship to the oil wellborehole so that a string of rods (as long as two miles) can be attachedto the reciprocating end of the walking beam with the other end attachedto a lift pump chamber at the bottom of the bore hole. A suitabledriving means, such as an electrical motor or internal combustionengine, is connected to a speed reduction unit which drives a crankwhich in turn is interconnected to the other end of the walking beam bya pitman.

[0005] Typically, pump-jack oil wells utilize an induction motor poweredby constant frequency, three-phase electrical power from a utility grid.The pump-jack pumping cycle varies the induction motor's speed onlyslightly as allowed by plus or minus a few percent of motor slip.However, the induction motor power typically varies over the pumpingcycle by about four (4) times the average motor power level. At two (2)points in the pumping cycle, the motor power requirement peaks and attwo (2) other points, the motor power requirements are at a minimum.Typically, at one of these minimum power requirement points in thepumping cycle, the induction motor extracts enough kinetic energy and/orwork from the moving masses of the well to be able to function as agenerator and produce electrical power which must be absorbed by theutility grid.

[0006] Whether the pump-jack oil well is driven by an induction motor orby an internal combustion engine, there is excess mechanical energy atsome point(s) in the pumping cycle which must be absorbed to preventexcessive velocity induced stresses in the pump-jack oil well movingparts. When a pump-jack oil well is powered by an internal combustionengine, engine compression is the means by which this energy isdissipated (compression losses) while in the normal utility grid poweredinduction motor system, the induction motor is periodically driven atoverspeed causing it to return power to the utility grid.

[0007] A micro turbogenerator with a shaft mounted permanent magnetmotor/generator can be utilized to provide electrical power for a widerange of utility, commercial and industrial applications. While anindividual permanent magnet turbogenerator may only generate 24 to 50kilowatts, powerplants of up to 500 kilowatts or greater are possible bylinking numerous permanent magnet turbogenerators together. Peak loadshaving power, grid parallel power, standby power, and remote location(stand-alone) power are just some of the potential applications forwhich these lightweight, low noise, low cost, environmentally friendly,and thermally efficient units can be useful.

[0008] The conventional power control system for a turbogeneratorproduces constant frequency, three-phase electrical power that closelyapproximates the electrical power produced by utility grids. If aturbogenerator with a conventional system for controlling its powergeneration were utilized to power a pump-jack type oil well, theturbogenerator's power capability would have to be sufficient to supplythe well's peak power requirements, that is, about four (4) times thewell's average power requirement. In other words, the turbogeneratorwould have to be about four (4) times as large, four (4) times as heavy,and four (4) times as expensive as a turbogenerator that only had toprovide the average power required by the oil well rather than thewell's peak power requirements.

[0009] There are other inherent difficulties present if a turbogeneratorwith a conventional power control system is used to provide electricalpower for a pump-jack type of oil well. If, for example, the oil well isin the part of the pumping cycle where it normally generates rather thanconsumes power, the operating speed of the rotating elements of theturbogenerator will tend to increase. The fuel control system of thepower control system will attempt to reduce the fuel flow to theturbogenerator combustor in order to prevent the turbogenerator'srotating elements from overspeeding which, in turn, risks quenching theflame in the combustor (flame out). A minimum fuel flow into thecombustor must be maintained to avoid flame out. This results in aminimum level of power generation, which together with the powerproduced by the oil well itself, must be deliberately dissipated aswasted power by the turbogenerator system, usually with a load resistorbut sometimes with a pneumatic load, either of which will reduce theturbogenerator system efficiency.

[0010] Also, when the power requirements for the oil well fall below thewell's peak requirement, the conventional turbogenerator control systemwill reduce the turbogenerator speed and the turbogenerator combustiontemperature. Since the present systems do not have any means todissipate excess power, the rapidly fluctuating load levels andunloading operation produce undesirable centrifugal and thermal cyclesstresses in many components of the turbogenerator system which will tendto reduce turbogenerator life, reliability and system efficiency.

[0011] When a pump-jack type oil well is powered by constant frequencyelectrical power from a utility grid or a conventionally controlledturbogenerator, the oil extraction pumping rate may not be sufficient tokeep up with the rate at which oil seeps into the well. In this case,potential oil production and revenues may be lost. Alternately, the oilextraction pumping rate may be greater than the rate at which oil seepsinto the well. In this case, the oil well may waste power when no oil isbeing pumped or it may be necessary to shut down the oil well for aperiod of time to allow more oil to seep into the well.

[0012] For the reasons stated above, the conventional turbogeneratorcontrol system is not generally suitable for pump-jack oil well systems.

SUMMARY OF THE INVENTION

[0013] The turbogenerator control system of the present inventionincludes a high frequency inverter synchronously connected to thepermanent magnet motor/generator of a turbogenerator, a low frequencyload inverter connected to the induction motor(s) of the pump-jack oilwell(s), a direct current bus electrically connecting the two (2)inverters, and a central processing unit which controls the frequencyand voltage/current of each of the inverters. This control system canreadily start the turbogenerator.

[0014] Alternately, a turbogenerator control system, when utilized togenerate power, can include a bridge rectifier which converts the highfrequency three-phase electrical power produced by the permanent magnetmotor/generator of the turbogenerator into direct current power, a lowfrequency load inverter connected to the induction motor(s) of thepump-jack oil well(s), a direct current bus electrically connecting therectifier to the low frequency load inverter and a central processingunit which controls the frequency and voltage/current of the lowfrequency load inverter. The configuration of this control system can bemodified by switching electrical contactors or relays to allow the lowfrequency load inverter to be used to start the turbogenerator.

[0015] Throughout the oil well's pumping cycle, the central processingunit increases or decreases the frequency of the low frequency loadinverter in order to axially accelerate and decelerate the masses of thedown hole steel pump rod(s) and oil and to rotationally accelerate anddecelerate the masses of the motor rotor and counter balance weights.

[0016] Precisely controlling the acceleration and deceleration of boththe axially moving and rotational moving masses of the oil well allowsrelatively independent control of the rate at which shaft power andelectrical power can be converted into kinetic energy. This kineticenergy can be cyclically stored by and extracted from the moving masses.Just as changing the rotational velocity versus time profile of thewell's rotating components allows the well to function as a conventionalflywheel, changing the normal axial velocity versus time profile of thewell's massive down hole moving components and oil, allows the well tofunction as an axial flywheel. Adjusting the frequency of the lowfrequency load inverter and the resulting speed of the well's inductionmotor also allows the oil pumping power to be controlled as a functionof time. The sum of the well's oil pumping power requirements and thepower converted into or extracted from the kinetic energies of themoving oil well masses is controlled so as to be nearly constant.

[0017] Thus, the combination of tailoring oil well pumping power as afunction of time and precisely controlling the insertion and extractionof kinetic energy into and out of the moving masses of oil wells resultsin stabilizing the power requirements demanded of a turbogeneratorpowering pump-jack oil wells. This in turn allows the size of theturbogenerator to be down sized by a factor of perhaps four to one (4 to1), avoids extreme variations in turbogenerator operating speed andcombustion temperature as well as avoids possible damage to theturbogenerator caused by cyclical variations in thermal and centrifugalstresses and possible damage to the controller/inverter electronicscaused by variation in turbogenerator voltage.

[0018] It is, therefore, a principal aspect of the present invention toprovide a system to control the operation of a turbogenerator and itselectronic inverters.

[0019] It is another aspect of the present invention to control the flowof fuel into the turbogenerator combustor.

[0020] It is another aspect of the present invention to control thetemperature of the combustion process in the turbogenerator combustorand the resulting turbine inlet and turbine exhaust temperatures.

[0021] It is another aspect of the present invention to control therotational speed of the turbogenerator rotor upon which the centrifugalcompressor wheel, the turbine wheel, the motor/generator, and thebearings are mounted.

[0022] It is another aspect of the present invention to control thetorque produced by the turbogenerator power head (turbine and compressormounted and supported by bearings on a common shaft) and delivered tothe motor/generator of the turbogenerator.

[0023] It is another aspect of the present invention to control theshaft power produced by the turbogenerator power head and delivered tothe motor/generator of the turbogenerator.

[0024] It is another aspect of the present invention to control theelectrical power produced by the motor/generator of the turbogenerator.

[0025] It is another aspect of the present invention to control theoperations of the high frequency inverter which inserts/extracts powerinto/from the motor/generator of the turbogenerator and produceselectrical power for the direct current bus of the turbogeneratorcontroller.

[0026] It is another aspect of the present invention to control theoperations of the low frequency load inverter which uses power from thedirect current bus of the turbogenerator controller to generate lowfrequency, three-phase power.

[0027] It is another aspect of the present invention to minimizevariations in the fuel flow rate into the turbogenerator combustor overthe operating cycle of a pump-jack oil well.

[0028] It is another aspect of the present invention to minimizevariations in the combustion and turbine temperatures of theturbogenerator over the operating cycle of a pump-jack oil well.

[0029] It is another aspect of the present invention to minimizevariations in the operating speed of the turbogenerator over theoperating cycle of a pump-jack oil well.

[0030] It is another aspect of the present invention to minimizevariations in the shaft torque generated by the turbogenerator powerhead and delivered to the motor/generator of the turbogenerator over theoperating cycle of a pump-jack oil well.

[0031] It is another aspect of the present invention to minimizevariations in the shaft power generated by the turbogenerator power headand delivered to the motor/generator of the turbogenerator over theoperating cycle of a pump-jack oil well.

[0032] It is another aspect of the present invention to minimizevariations in the level of electrical power extracted from themotor/generator of the turbogenerator and converted into direct currentpower by the high frequency inverter, or the bridge rectifier, over theoperating cycle of a pump-jack oil well.

[0033] It is another aspect of the present invention to minimizevariations in the level of electrical power extracted from the directcurrent bus and converted into low frequency, three-phase power by thelow frequency load inverter over the operating cycle of a pump-jack oilwell.

[0034] It is another aspect of the present invention to minimizevariations in the level of electrical power delivered to, and utilized,the induction motor(s) of the pump-jack oil well(s) over the operatingcycle of a pump-jack oil well.

[0035] It is another aspect of the present invention to provide acontrol system that sets the average frequency of the low frequency loadinverter over the operating cycle of a pump-jack oil well.

[0036] It is another aspect of the present invention to provide acontrol system where the average frequency of the low frequency loadinverter over the operating cycle of a pump-jack oil well can be set sothat the oil pumping rate of the well is matched to the rate at whichoil seeps into the well from the surrounding oil ladened matrix. Thus,the well neither runs dry nor has to produce oil at less than the well'scapacity.

[0037] It is another aspect of the present invention to provide acontrol system that varies the instantaneous frequency of the lowfrequency load inverter over the operating cycle of a pump-jack oilwell.

[0038] It is another aspect of the present invention to provide acontrol system that varies the instantaneous voltage or current of thelow frequency load inverter over the operating cycle of a pump-jack oilwell.

[0039] It is another aspect of the present invention to provide acontrol system where the variation in the instantaneous frequency of thelow frequency load inverter over the operating cycle of a pump-jack oilwell is the primary means by which the system reduces the variations inpower required by the induction motor of the pump-jack oil well.

[0040] It is another aspect of the present invention to provide acontrol system where the variation in the voltage or current of the lowfrequency load inverter over the operating cycle of a pump-jack oil wellis the secondary means by which the system reduces the variations inpower required by the induction motor of the pump-jack oil well andsimultaneously is the primary means by which the system controls theslip and maximizes the efficiency of the induction motor.

[0041] It is another aspect of the present invention to provide acontrol system with that can precisely control the insertion of kineticenergy into, and the extraction of kinetic energy from, the movingmasses of the pump-jack oil well over the operating cycle of the well.

[0042] It is another aspect of the present invention to provide acontrol system that allows the rotational moving masses of the pump-jackoil well to function as a flywheel for energy storage.

[0043] It is another aspect of the present invention to provide acontrol system that allows the axially moving masses of the pump-jackoil well to function as an axial flywheel for energy storage.

[0044] It is another aspect of the present invention to provide acontrol system that can precisely control the instantaneous pumping workbeing performed by a pump-jack oil well or the instantaneous pumpingwork being extracted from a pump-jack oil well over the operating cycleof that well.

[0045] It is another aspect of the present invention to provide acontrol system that causes the total of the instantaneous pumping energyrequired/produced by pump-jack oil well(s) and the instantaneous kineticenergy extracted/inserted from/into pump-jack oil well(s) to be nearlyconstant over the operating cycle of the well(s).

[0046] It is another aspect of the present invention to provide acontrol system that utilizes the phase relationship of the pump-jack oilwell induction motor voltage and current to both measure the resonantvelocities of the down hole rod string and to damp these resonances withappropriate modulations in the torque of the induction motor.

[0047] It is another aspect of the present invention to provide acontrol system that soft clamps the maximum and minimum frequencies ofthe low frequency load inverter to avoid excessive rod stresses at highfrequencies, to avoid oil well pumping direction reversals and tosimultaneously minimize the excitation of rod string resonances.

[0048] It is another aspect of the present invention to provide acontrol system that soft clamps the maximum voltage of the low frequencyload inverter to avoid excessive voltage stresses on inverter and motorcomponents while simultaneously minimizing the excitation of rod stringresonances.

[0049] It is another aspect of the present invention to provide acontrol system that soft clamps the D.C. bus voltage for safety.

[0050] It is another aspect of the present invention to provide acontrol system that minimizes thermal and centrifugal stress cycledamage to the turbogenerator's combustor, recuperator, turbine wheel,compressor wheel, and other components that can be caused by variationsin turbogenerator operating power level, speed or temperature and whichare, in turn, induced by the cyclical nature of pump-jack operation.

[0051] It is another aspect of the present invention to provide acontrol system that minimizes the risk of combustor flame out that canoccur when conventional turbogenerator fuel control systems reducecombustor fuel flow when the pump-jack's power requirements are at aminimum or are reversed during the pumping cycle.

[0052] It is another aspect of the present invention to provide acontrol system that avoids the need for parasitic loads with theirresulting inefficiencies and avoids the inefficiencies associated withoff optimum operations when fuel flow, temperature, and speed varywidely.

[0053] It is another aspect of the present invention to provide acontrol system that allows the peak electrical power required by apump-jack oil well to be reduced by a factor of about four to one.

[0054] It is another aspect of the present invention to provide acontrol system that allows the size, weight, and cost of aturbogenerator that powers a pump-jack oil well to be reduced by afactor of about four to one.

[0055] It is another aspect of the present invention to provide acontrol system that allows the size, weight, and cost of the inductionmotor utilized by a pump-jack oil well to be reduced by a factor ofabout four to one.

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Having thus described the present invention in general terms,reference will now be made to the accompanying drawings in which:

[0057]FIG. 1 is a perspective view, partially cut away, of a permanentmagnet turbogenerator/motor for use with the power control system of thepresent invention;

[0058]FIG. 2 is a functional block diagram of the interface between aturbogenerator/motor controller and the permanent magnetturbogenerator/motor illustrated in FIG. 1;

[0059]FIG. 3 is a functional block diagram of the permanent magnetturbogenerator/motor controller of FIG. 2;

[0060]FIG. 4 is a functional block diagram of the interface between analternate turbogenerator/motor controller and the permanent magnetturbogenerator/motor illustrated in FIG. 1;

[0061]FIG. 5 is a functional block diagram of the permanent magnetturbogenerator/motor controller of FIG. 4;

[0062]FIG. 6 a plan view of a pump-jack oil well system for use with thepower control system of the present invention;

[0063]FIG. 7 is a graph of power requirements in watts versus operatingtime in seconds for the pump-jack oil well system of FIG. 6;

[0064]FIG. 8 is a functional block diagram of the basic power controlsystem of the present invention; and

[0065]FIG. 9 is a detailed functional block diagram of the power controlsystem of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] A permanent magnet turbogenerator/motor 10 is illustrated in FIG.1 as an example of a turbogenerator/motor for use with the power controlsystem of the present invention. The permanent magnetturbogenerator/motor 10 generally comprises a permanent magnet generator12, a power head 13, a combustor 14 and a recuperator (or heatexchanger) 15.

[0067] The permanent magnet generator 12 includes a permanent magnetrotor or sleeve 16, having a permanent magnet disposed therein,rotatably supported within a permanent magnet motor stator 18 by a pairof spaced journal bearings. Radial stator cooling fins 25 are enclosedin an outer cylindrical sleeve 27 to form an annular air flow passagewhich cools the stator 18 and thereby preheats the air passing throughon its way to the power head 13.

[0068] The power head 13 of the permanent magnet turbogenerator/motor 10includes compressor 30, turbine 31, and bearing rotor 36 through whichthe tie rod 29 passes. The compressor 30, having compressor impeller orwheel 32 which receives preheated air from the annular air flow passagein cylindrical sleeve 27 around the permanent magnet motor stator 18, isdriven by the turbine 31 having turbine wheel 33 which receives heatedexhaust gases from the combustor 14 supplied with air from recuperator15. The compressor wheel 32 and turbine wheel 33 are rotatably supportedby bearing shaft or rotor 36 having radially extending bearing rotorthrust disk 37. The bearing rotor 36 is rotatably supported by a singlejournal bearing within the center bearing housing while the bearingrotor thrust disk 37 at the compressor end of the bearing rotor 36 isrotatably supported by a bilateral thrust bearing. The bearing rotorthrust disk 37 is adjacent to the thrust face of the compressor end ofthe center bearing housing while a bearing thrust plate is disposed onthe opposite side of the bearing rotor thrust disk 37 relative to thecenter housing thrust face.

[0069] Intake air is drawn through the permanent magnet generator 12 bythe compressor 30 which increases the pressure of the air and forces itinto the recuperator 15. In the recuperator 15, exhaust heat from theturbine 31 is used to preheat the air before it enters the combustor 14where the preheated air is mixed with fuel and burned. The combustiongases are then expanded in the turbine 31 which drives the compressor 30and the permanent magnet rotor 16 of the permanent magnet generator 12which is mounted on the same shaft as the turbine wheel 33. The expandedturbine exhaust gases are then passed through the recuperator 15 beforebeing discharged from the turbogenerator/motor 10.

[0070] The interface between the turbogenerator/motor controller 40 andthe permanent magnet turbogenerator/motor 10 is illustrated in FIG. 2.The controller 40 generally comprises two bi-directional inverters, alow frequency load inverter 144 and a generator inverter 146. Thecontroller 40 receives electrical power 41 from a source such as autility through AC filter 51 or alternately from a battery throughbattery control electronics 71. The generator inverter 146 starts theturbine 31 of the power head 13 (using the permanent magnet generator asa motor) form either utility or battery power, and then the lowfrequency load inverter 144 produces AC power using the output powerfrom the generator inverter 146 to draw power from the high speedpermanent magnet turbogenerator 10. The controller 40 regulates fuel tothe combustor 14 through fuel control valve 44.

[0071] The controller 40 is illustrated in more detail in FIG. 3 andgenerally comprises the insulated gate bipolar transistors (IGBT) gatedrives 161, control logic 160, generator inverter 146, permanent magnetgenerator filter 180, DC bus capacitor 48, low frequency load inverter144, AC filter 51, output contactor 52, and control power supply 182.The control logic 160 also provides power to the fuel cutoff solenoid62, the fuel control valve 44 and the ignitor 60. The battery controller71 connects directly to the DC bus. The control logic 160 receivestemperature signal 164, voltage signal 166, and current signal 184 whileproviding a relay drive signal 165.

[0072] Control and start power can come from either the external batterycontroller 71 for battery start applications or from the utility 41which is connected to a rectifier using inrush limiting techniques toslowly charge the internal bus capacitor 48. For grid connectapplications, the control logic 160 commands gate drives 161 and thesolid state (IGBT) switches associated with the low frequency loadinverter 144 to provide start power to the generator inverter 146. TheIGBT switches are operated at a high frequency and modulated in a pulsewidth modulation manner to provide four quadrant inverter operationwhere the inverter 144 can either source power from the DC link to thegrid or source power from the grid to the DC link. This control may beachieved by a current regulator. Optionally, two of the switches mayserve to create an artificial neutral for stand-alone operations.

[0073] The solid state (IGBT) switches associated with the generatorinverter 146 are also driven from the control logic 160 and gate drives161, providing a variable voltage, variable frequency, three-phase driveto the generator motor 10 to start the turbine 31. The controller 40receives current feedback 184 via current sensors when the turbinegenerator has been ramped up to speed to complete the start sequence.When the turbine 31 achieves self-sustaining speed, the generatorinverter 146 changes its mode of operation to boost the generator outputvoltage and provide a regulated DC link voltage.

[0074] The generator filter 180 includes a plurality of inductors toremove the high frequency switching components from the permanent magnetgenerator power so as to increase operating efficiency. The AC filter 51also includes a plurality of inductors plus capacitors to remove thehigh frequency switching components. The output contactor 52 disengagesthe low frequency load inverter 144 in the event of a unit fault.

[0075] The fuel solenoid 62 is a positive fuel cutoff device which thecontrol logic 160 opens during the start sequence and maintains openuntil the system is commanded off. The fuel control valve 44 is avariable flow valve providing a dynamic regulating range, allowingminimum fuel during start and maximum fuel at full load. A variety offuel controllers, including liquid and gas fuel controllers may beutilized. The ignitor 60 would normally be a spark type device, similarto a spark plug for an internal combustion engine. It would, however,only be operated during the start sequence.

[0076] For stand-alone operation, the turbine is started using anexternal DC converter which boosts voltage from an external source suchas a battery and connects directly to the DC link. The low frequencyload inverter 144 can then be configured as a constant voltage, constantfrequency source. However, the output is not limited to being a constantvoltage, constant frequency source, but rather may be a variablevoltage, variable frequency source. For rapid increases in output powerdemand, the external DC converter supplies energy temporally to the DClink and to the power output, the energy is then restored to the energystorage and discharge system 69 after a new operating point is achieved.

[0077] A functional block diagram of the interface between the alternatecontroller 40′ and the permanent magnet turbogenerator/motor 10 forstand-alone operation is illustrated in FIG. 4. The generator controller40′ receives power from a source such as a utility or battery system tooperate the permanent magnet generator 12 as a motor to start rotationof compressor 30 and turbine 31 of the power head 13. During the startsequence, the utility power 41 if available, is rectified and acontrolled frequency ramp is supplied to the permanent magnet generator12 which accelerates the permanent magnet rotor 16, the compressor wheel32, bearing rotor 36 and turbine wheel 33. This acceleration provides anair cushion for the air bearings and airflow for the combustion process.At about 12,000 rpm, spark and fuel are provided to the combustor 14 andthe generator controller 40′ assists acceleration of the turbogenerator10 up to about 40,000 rpm to complete the start sequence. The fuelcontrol valve 44 is also regulated by the generator controller 40′.

[0078] Once self sustained operation is achieved, the generatorcontroller 40′ is reconfigured to produce low frequency, variablevoltage three-phase AC power (up to 250 VAC for 208 V systems, up to 550VAC for 480 V systems) 42 from the rectified high frequency AC output(280-380 volts for 208 V systems, 600-900 volts for 480 V systems) ofthe high speed permanent magnet turbogenerator 10 to supply the needs ofthe pump-jack oil well induction motor. The permanent magnetturbogenerator 10 is commanded to a power set point with fuel flow,speed, and combustion temperature varying as a function of the desiredoutput power.

[0079] The generator controller 40′ also includes an energy storage anddischarge system 69 having an ancillary electric storage device 70 whichis connected through control electronics 71. This connection isbi-directional in that electrical energy can flow from the ancillaryelectric storage device 70 to the generator controller 40′, for exampleduring turbogenerator/motor start-up, and electrical energy can also besupplied from the turbogenerator/motor controller 40′ to the ancillaryelectric storage device or battery 70 during sustained operation.

[0080] An example of this alternate turbogenerator/motor control systemis described in U.S. patent application Ser. No. 003,078, filed Jan. 5,1998 by Everett R Geis, Brian W. Peticolas, and Joel B. Wacknov entitled“Turbogenerator/Motor Controller with Ancillary EnergyStorage/Discharge”, assigned to the same assignee as this applicationand incorporated herein by reference.

[0081] The functional blocks internal to the generator controller 40′are illustrated in FIG. 5. The generator controller 40′ includes inseries the start power contactor 46, bridge rectifier 47, DC buscapacitors 48, pulse width modulated (PWM) inverter 49, AC output filter51, output contactor 52, generator contactor 53, and permanent magnetgenerator 12. The generator rectifier 54 is connected from between thebridge rectifier 47 and bus capacitors 48 to between the generatorcontactor 53 and permanent magnet generator 12. The AC power output 42is taken from the output contactor 52 while the neutral is taken fromthe AC filter 51.

[0082] The control logic section consists of control power supply 56,control logic 57, and solid state switched gate drives illustrated asintegrated gate bipolar transistor (IGBT) gate drives 58, but may bedrives for any high speed solid state switching device. The controllogic 57 receives a temperature signal 64 and a current signal 65 whilethe IGBT gate drives 58 receive a voltage signal 66. The control logic57 sends control signals to the fuel cutoff solenoid 62, the fuelcontrol valve(s) 44 (which may be a number of electrically controlledvalves), the ignitor 60 and compressor discharge air dump valve 61. ACpower 41 is provided to both the start power contactor 46 and in someinstances directly to the control power supply 56 in the control logicsection of the generator controller 40′ as shown in dashed lines.

[0083] The energy storage and discharge system 69 is connected to thecontroller 40′ across the voltage bus V_(bus) between the bridgerectifier 47 and DC bus capacitor 48 together with the generatorrectifier 54. The energy storage and discharge system 69 includes anoff-load device 73 and ancillary energy storage and discharge switchingdevices 77 both connected across voltage bus V_(bus).

[0084] The off-load device 73 includes an off-load resistor 74 and anoff-load switching device 75 in series across the voltage bus V_(bus).The ancillary energy storage and discharge switching device 77 comprisesa charge switching device 78 and a discharge switching device 79, alsoin series across the voltage bus V_(bus). Each of the charge anddischarge switching devices 78, 79 include solid state switches 81,shown as an integrated gate bipolar transistor (IGBT) and anti-paralleldiodes 82. Capacitor 84 and ancillary storage and discharge device 70,illustrated as a battery, are connected across the discharge switchingdevice 79 with main power relay 85 between the capacitor 84 and theancillary energy storage and discharge device 70. Inductor 83 isdisposed between the charge switching device 78 and the capacitor 84. Aprecharge device 87, consisting of a precharge relay 88 and prechargeresistor 89, is connected across the main power relay 85.

[0085] The PWM inverter 49 operates in two basic modes: a variablevoltage (0-190 V line to line), variable frequency (0-700 Hertz)constant volts per Hertz, three-phase mode to drive the permanent magnetgenerator/motor 12 for start up or cool down when the generatorcontactor 53 is closed; or a constant voltage (120 V line to neutral perphase), constant frequency three-phase 60 Hertz mode. The control logic57 and IGBT gate drives 58 receive feedback via current signal 65 andvoltage signal 66, respectively, as the turbine generator is ramped upin speed to complete the start sequence. The PWM inverter 49 is thenreconfigured to provide 60 Hertz power, either as a current source forgrid connect, or as a voltage source.

[0086] The PWM inverter 49 is truly a dual function inverter which isused both to start the permanent magnet turbogenerator/motor 10 and toconvert the permanent magnet turbogenerator/motor output to utilitypower, either as sixty Hertz, three-phase, constant voltage for standalone applications, or as a sixty Hertz, three-phase, current source forgrid parallel applications. With start power contactor 46 closed, singleor three-phase utility power is brought to bridge rectifier 47 andprovide precharged power and then start voltage to the bus capacitors 48associated with the PWM inverter 49. This allows the PWM inverter 49 tofunction as a conventional adjustable speed drive motor starter to rampthe permanent magnet turbogenerator/motor 10 up to a speed sufficient tostart the gas turbine 31.

[0087] An additional rectifier 54, which operates from the output of thepermanent magnet turbogenerator/motor 10, accepts the three-phase power,(up to 380 volt AC) from the permanent magnet generator/motor 12 (whichat fill speed produces 1600 Hertz power). This diode is classified as afast recovery diode rectifier bridge. Six diode elements arranged in aclassic bridge configuration comprise this high frequency rectifier 54which provides output power DC to power the inverter. Alternately, therectifier 54 may be replaced with a high speed inverter permanentlyconnected to the turbogenerator, eliminating the dual functionality ofthe inverter 49, and eliminating the need for certain contactors, suchas generator contactor 53. The rectified voltage is as high as 550 voltsunder no load.

[0088] The off-load device 73, including off-load resistor 74 andoff-load switching device 75 can absorb thermal energy from theturbogenerator 10 when the load terminals are disconnected, or there isa rapid reduction in load power demand. The off-load switching device 75will turn on proportionally to the amount of off-load required andessentially will provide a load for the gas turbine 31 while the fuel isbeing cut back to stabilize operation at a reduce power level. Thesystem serves as a dynamic brake with the resistor connected across theDC bus through an IGBT and serves as a load on the gas turbine duringany overspeed condition.

[0089] In addition, the ancillary electric storage device 70 cancontinue motoring the turbogenerator 10 for a short time after ashutdown in order to cool down the turbogenerator 10 and prevent thesoak back of heat from the recuperator 15. By continuing the rotation ofthe turbogenerator 10 for several minutes after shutdown, the power head13 will keep moving air through the turbogenerator which will sweep heataway from the permanent magnet generator 12 and compressor wheel 32.This allows a gradual and controlled cool down of all of the turbine endcomponents.

[0090] The battery switching devices 77 are a dual path since theancillary electric storage device 70 is bi-directional. The ancillaryelectric storage device 70 can provide energy to the power inverter 49when a sudden demand or load is required and the gas turbine 31 is notup to speed. At this point, the battery discharge switching device 79turns on for a brief instant and draws current through the inductor 83.The battery discharge switching device 79 is then opened and the currentpath continues by flowing through the diode 82 of the battery chargeswitching device 78 and then in turn provides current into the invertercapacitor 48.

[0091] The battery discharge switching device 79 is operated at avarying duty cycle, high frequency, rate to control the amount of powerand can also be used to initially ramp up the controller 40′ voltageduring battery start operations. After the system is in a stabilized,self-sustaining condition, the battery charge switching device 78 isused in an opposite manner. At this time, the battery charge switchingdevice 78 periodically closes in a high frequency modulated fashion toforce current through inductor 83 and into capacitor 84 and thendirectly into the ancillary electric storage device 70.

[0092] The capacitor 84, connected to the ancillary electric storagedevice 70 via the precharge relay 88 and resistor 89 and the main powerrelay 85, is provided to buffer the ancillary electric storage device70. The normal, operating sequence is that the precharge relay 88 ismomentarily closed to allow charging of all of the capacitive devices inthe entire system and then the main power relay 85 is closed to directlyconnect the ancillary electric storage device 70 with the controlelectronics 71. While the main power relay 85 is illustrated as aswitch, it may also be a solid state switching device.

[0093]FIG. 6 generally illustrates a pump-jack oil well system with apumping unit 110 having a driving means 111 connected thereto with theapparatus suitably supported on base 112. A Samson post 113 supports awalking beam 114 which is pivotably affixed thereto by a saddle 115which forms a journal.

[0094] The walking beam 114 has a horse-head attachment 116 at one endthereof so that a cable 117 can be connected at yoke 118 (including aload cell to provide real time monitoring of the rod load and itsdynamic behavior including its resonant frequencies and resonantmotions) to a polished rod 119 to enable a rod string located downholein the well bore 120 to be reciprocated. The other end 121 of thewalking beam 114 is journaled at 122 to a pitman or connecting rod 123.The other end of the connecting rod 123 is affixed to a crank 124 bymeans of journal 125. The crank 124 is affixed to a power output driveshaft 126 of a reduction gear assembly 127 with a counterbalance 128affixed along a marginally free end portion of the crank 124.

[0095] The gear reducer 127 is mounted on a support 129 which is in turnmounted on the base 112. Driven gear or pulley 130 is attached by meansof belts or chains 131 to the drive gear or pulley 132 which in turn issupported at 133 from base 134. An electrical induction motor 137 isadjustably mounted by hinge means on the support 133. The electricalinduction motor 137 may include a rotating inertial mass 138.

[0096]FIG. 7 illustrates a graph of power requirements in watts versusoperating time in seconds for the pump-jack oil well system generallydescribed in FIG. 6 with power supplied from a utility grid. Region “A”represents the start of the pump-jack stroke. The crank arm 124 andcounterweight 128 of the pump-jack passes through top dead center andthe sucker rod begins its upward travel at approximately top deadcenter, depending on the exact positioning of the crankshaft center 126with respect to the beam journal 122, and may be several degrees eitherside of top dead center. The induction motor power flows to thepump-jack until the crank arm is approximately thirty (30) degrees aftertop dead center at which point energy from the falling counterweightbegins to contribute significantly to the liquid load pumping power(displacing motor power)

[0097] In region “B”, energy released by the falling counterweight onthe crank arm exceeds the liquid pumping load and tries to overspeed thedrive motor turning it into a generator. During this period, electricalpower is exported to the utility grid. In region “C”, the counterweighthas passed through bottom dead center and is rising. The sucker rod istravelling down under its own weight and the motor power goes almostexclusively to lifting the counterweight. Region “D” represents theperiod of time in the cycle when the counterweight is being raised andthe sucker rod lowered while the liquid lift load occurs during Region“E”.

[0098] More specifically, bottom dead center on the crank arm occurs atapproximately five (5) seconds on the above scale. Between five andone-half (5½) seconds and eight and one-half (8½) seconds, thecounterweight is being raised as the sucker rod lowers. The peakelectrical demand of approximately twenty-six (26) kWe occurs nearlyninety (90) degrees after bottom dead center. At eight and one-half (8½)seconds, the counterweight crosses top dead center where the liquid loadis imposed.

[0099] At this point, there is little energy available from thecounterweight as it is moving essentially horizontal so a secondarypower peak occurs as liquid is being lifted before the counterweightbegins to fall. At eleven (11) seconds, the falling counterweightdelivers more power (torque) than required for liquid lift and the motoroverspeeds (slightly) turning the motor into a generator that brakes thecounterweight. Peak power generated is approximately eight (8) kW. Aboutthirty (30) degrees after bottom dead center, the crank slows to belowsynchronous speed for the motor at which point power is required to liftthe counterweight again.

[0100] The basic power control system of the present invention isillustrated in block diagram form in FIG. 8. The power control systemincludes the turbogenerator controller 40 or 40′, the turbogenerator 10,the pump-jack induction motor 137, and the pump-jack oil well 110. Thecontroller 40 or 40′ regulates the turbogenerator speed required toproduce the power required by the pump-jack by varying the fuel flow tothe turbogenerator combustor 14 while the controller 40 or 40′specifically varies the output frequency of inverter 144 or 49 and thespeed of the pump-jack induction motor 137 to control the load power andto maintain turbogenerator operation within overspeed, combustor flameout and overtemperature limits.

[0101]FIG. 9 illustrates a more detailed functional block diagram of thepower control system of the present invention which includes threeprimary control loops used to regulate the turbogenerator gas turbineengine. The three primary control loops are the turbine exhaust gastemperature control loop 200, the turbogenerator speed control loop 202,and the power control loop 204. The speed control loop 202 commands fueloutput to the turbogenerator fuel control 44 to regulate the rotatingspeed of the turbogenerator 10. The turbine exhaust gas temperaturecontrol loop 200 commands fuel output to the fuel control 44 to regulatethe operating temperature of the turbogenerator 10. The minimum fuelcommand 210 is selected by selector 212 which selects the least signalfrom the speed control loop 202 and the turbine exhaust gas temperaturecontrol loop 200.

[0102] The pump-jack load profile, as illustrated in FIG. 7, consists ofperiods of variable load and periods of regenerative power generation(region B of FIG. 7). The possibility of turbogenerator overspeed canresult, particularly when a stored thermal energy device such as arecuperator 15 is utilized as part of the turbogenerator 10. To preventthis overspeed and maximize the overall system efficiency, the pump-jackspeed can be increased to provide an inertial load and an increased oilpumping load which counter the regenerative load.

[0103] This is accomplished in part by a maximum turbogenerator speedcontrol loop 214 that varies the frequency command to the low frequencyload inverter 144 or to the variable speed inverter 49, which varies thespeed of the induction motor 137 of the pump-jack 110. The frequencyoffset signal 279 is produced from limitor 287. In addition, the speedof the pump-jack induction motor 137 can be varied to control maximum ortransient turbine exhaust gas temperature by a maximum turbine exhaustgas temperature control loop 216. The frequency offset signal 218 isproduced from limitor 280.

[0104] The turbogenerator power control system of the present inventionand the turbogenerator 10 which it controls are capable of beingutilized by pump-jack oil well operators without the need for anyspecial training. The turbogenerator 10 and control system are alsocapable of being moved from one group of one or more oil wells toanother group of wells without any requirement to manually change any ofthe control system parameters.

[0105] The power control system can automatically adapt itself topowering any number of wells from one to the maximum number of oil wellspermitted by the power level available from the turbogenerator 10 andcan tolerate all of the oil wells requiring peak power at the same timeor having peak power requirements staggered in time (out of phase). Itcan tolerate the total power required by the oil wells that it suppliesbeing near the peak power capability of the turbogenerator 10 or beingzero (e.g. with open circuit breakers), or anywhere in between.

[0106] As illustrated in FIG. 9, the average frequency 240 that isdesired for the three-phase electrical power produced by the lowfrequency or load inverter 144 (or 49) is compared in summer orcomparator 242 with the instantaneous frequency 243 produced by theinverter 144 (or 49). The difference in these frequency values, theerror signal 244, is utilized as the input to a turbogenerator speedcommand control loop 230 and a turbogenerator power command control loop232. When the average over time of the error signal 244 is zero, thepower utilized by the oil wells is equal to the power generated by theturbogenerator 10.

[0107] The turbogenerator speed command control loop 230, includingproportional integral control 231, generates a recommended speed signal245 for the turbogenerator 10 that should produce a level of electricalpower equal to the power utilized by the oil wells. This recommendedspeed signal 245 is limited by limitor 246 to a maximum value equal tothe maximum safe operating speed of the turbogenerator 10 and also islimited by the limitor 246 to a minimum value equal to the minimum speedat which the turbogenerator 10 can operate with no power output.

[0108] The proportional integral control 233 of the power commandcontrol loop 232 establishes a recommended power consumption levelsignal 234 for the oil wells that should match the level of electricalpower produced by the turbogenerator 10. This recommended powerconsumption level signal 234 is limited by limitor 236 to a maximumvalue equal to the maximum power that can be produced by theturbogenerator 10 and is further limited by limitor 236 to a minimumvalue equal to zero when the oil well's circuit breakers are open.

[0109] The output signal 247 from the speed command control loop 230constitutes a speed command 247 to the turbogenerator 10. This speedcommand 247 is compared in comparator 248 against the realturbogenerator speed feedback signal 206 from the turbogenerator 10. Theerror signal 249 between these two speed values is fed to theproportional integral control 203 of the speed control loop 202 toproduce a recommended fuel flow 258.

[0110] The look up table 208 is used together with the realturbogenerator speed feedback signal 206 from the turbogenerator 10 toestablish the recommended turbine exhaust gas temperature command 250for the turbine. This recommended turbine exhaust gas temperaturecommand 250 is compared in comparator 251 against the real turbineexhaust gas temperature feedback signal 207 from the turbogenerator 10to produce a computed turbine exhaust gas temperature error signal 252.This computed turbine exhaust gas temperature error signal 252 ininputted to proportional integral control 254 in the turbine exhaust gastemperature loop 200 which computes a recommended fuel flow signal 256that should eliminate the temperature error.

[0111] Selector 212 selects the lowest of the signals from the turbineexhaust gas temperature loop 200 and the speed control loop 202 andprovides the lower signal to the limitor 260 which limits therecommended fuel flow to a maximum value equal to that required toproduce the maximum power that the turbogenerator 10 produces and to aminimum value equal to the fuel flow below which the combustor 14 willexperience flame out. The selected fuel flow value 262 is then used bythe fuel control 44 to determine/deliver the required fuel flow rate tothe combustor 14. The resulting turbogenerator speed feedback signal 206and turbine exhaust gas temperature feedback signal 207 are measured atthe turbogenerator 10 and utilized elsewhere in the power controlsystem.

[0112] The output 237 from limitor 236 constitutes the low frequencyload inverter 144 (or 49) average power command which is compared incomparator 264 with the real instantaneous power feedback signal 265from the power sensor 270. The resulting error signal 266 is utilized inproportional integral control 268 to produce a recommended instantaneousinverter frequency signal 269 that should eliminate the power error.

[0113] Comparator 271 compares the speed feedback signal 206 from theturbogenerator 10 with the maximum safe speed signal 272 for theturbogenerator 10 to produce a speed error signal 273. If the speed ofthe turbogenerator 10 is greater than the maximum safe speed 272, theproportional integral control 274 establishes a recommended frequencyincrease signal 279 (limited in limitor 287) in the low frequency loadinverter frequency and hence the pump-jack oil well speed that shouldeliminate the turbogenerator overspeed.

[0114] The turbine exhaust gas temperature feedback signal 207 from theturbogenerator 10 is compared with the maximum safe turbine exhaust gastemperature signal 275 in comparator 276 to produce an error signal 277.If the turbine exhaust gas temperature of the turbogenerator 10 isgreater than the maximum safe temperature 275, the proportional integralcontrol 278 establishes a recommended frequency increase signal 218(limited in limitor 280) in the low frequency load inverter frequencyand hence the pump-jack oil well speed that should eliminate the overtemperature.

[0115] Both of the two inverter frequency reduction signals 279 and 218are provided to comparator or summer 282 which also receives signal 269.The error signal 291 from summer 282 is provided to limitor 289 beforegoing to the inverter 144 or inverter 49. This limited error signalcontrols the frequency of the inverter 144 and provides a frequencylimit signal 243 to both comparator 242 and to the look up table 290which computes the inverter output voltage.

[0116] The turbogenerator 10 and pump-jack oil wells 110 aredeliberately operated at nearly constant power over the oil well'spumping cycle. Since, however, induction motors nominally have a powercapability that is proportional to the motor's speed and the inductiveimpedance and the electromotive force generated voltage of the inductionmotor for constant current are both nominally proportional to inverterfrequency and motor speed, operating the induction motor at constantvoltage as the inverter/motor frequency varies can produce unacceptableresults. Such operation can, for instance, cause the motor laminationsto magnetically saturate at low frequency/speed, resulting in excessivecurrent/heating and stator winding damage. Varying induction motorvoltage approximately with the square root of inverter frequency is aviable alternative and allows the induction motor slip to be a lowexponential (e.g. 0.5) inverse function of frequency/speed (the lowerthe frequency/speed the greater the slip).

[0117] The three-phase electrical power produced by the low frequencyload inverter 144 passes through the power sensor 270. The signal 265from the power sensor 270 is utilized by comparator 264 to assure thatthe power delivered by the low frequency inverter 144 to the pump-jackinduction motor 137 is equal to the turbogenerator/motor power that isrequired to maintain the low frequency load inverter's average frequencyat the desired level.

[0118] The desired average frequency of the low frequency load inverter144 can be set equal to utility frequency (e.g. 50 or 60 Hertz) or itcan be set to assure that the oil well pumps oil at the same rate as theoil seeps into the well from the surrounding strata.

[0119] Relatively independent control of the rate at which shaft powerand electrical power can be converted into kinetic energy can beachieved by precisely controlling the acceleration and deceleration ofboth the axially moving and rotationally moving masses of the oil well.This kinetic energy can be cyclically stored by and extracted from themoving masses. In other words, changing the normal axial velocity versustime profile of the well's massive down hole moving components and oilallows the well to function as what can best be described as an “axialflywheel”. Adjusting the frequency of the low frequency load inverterand the resulting speed of the well's induction motor also allows theoil pumping power to be controlled as a function of time. The sum of thewell's oil pumping power requirements and the power converted into andextracted from the kinetic energies of the moving oil well masses iscontrolled so as to be nearly constant. Without this control system thepower requirements of this type of oil well can vary over severalseconds (typically eight (8)) by up to four (4) times the average powerrequired by the well. This means that the size of the turbogeneratormight otherwise have to be increased by a factor of four (4) and theturbogenerator might otherwise experience cyclical variations inoperating speed and temperature, suffer excessive centrifugal andthermal stresses, and operate unstably and operate with low efficiency.

[0120] The improved power control system for the turbogenerator willallow a turbogenerator to provide electrical power to one or moreperiodically varying loads, such as the induction motors of pump-jacktype oil wells, without the need to vary turbogenerator operating speed,fuel consumption or combustion temperature.

[0121] The required induction motor speed variances can be decreased byincreasing induction motor inertia, for example, by the use of theinertial mass 138. Varying pump speed, augmenting inertia energystorage, and/or using an electrical energy storage device can all beused individually or in any combination to resolve energy regenerationand/or flatten the induction motor load profile.

[0122] While specific embodiments of the invention have been illustratedand described, it is to be understood that these are provided by way ofexample only and that the invention is not to be construed as beinglimited thereto but only by the proper scope of the following claims.

What we claim is:
 1. In combination: a permanent magnetturbogenerator/motor; a repetitive axial motion machine driven by anelectric motor supplied with electrical power by said permanent magnetturbogenerator/motor, and a controller operably associated with saidpermanent magnet turbogenerator/motor and said repetitive axial motionmachine to establish a variable frequency time profile for said electricmotor of said repetitive axial motion machine which provides a generallyconstant power level for said permanent magnet turbogenerator/motor. 2.The combination of claim 1 wherein said controller includes; a highfrequency inverter synchronously connected to said permanent magnetturbogenerator/motor; a low frequency load inverter operably connectedto said electric motor driving said repetitive axial motion machine; adirect current bus electrically connecting said high frequency inverterwith said low frequency load inverter; and a processor to control thefrequency and voltage/current of said high frequency inverter and saidlow frequency load inverter.
 3. The combination of claim 1 wherein saidcontroller includes; a bridge rectifier connected to said permanentmagnet turbogenerator/motor to convert the high frequency three-phaseelectrical power produced by said turbogenerator into direct currentpower; a low frequency load inverter operably connected to said electricmotor driving said repetitive axial motion machine; a direct current buselectrically connecting said bridge rectifier with said low frequencyload inverter; and a processor to control the frequency andvoltage/current of said low frequency load inverter.
 4. The combinationof claim 2 wherein said repetitive axial motion machine driven by anelectric motor is a pump-jack oil well having axial and rotationalmasses, and said processor varies the frequency of said low frequencyload inverter to accelerate and decelerate said axial and rotationalmasses of said pump-jack oil well to control the power requirements ofsaid electric motor driving said pump-jack oil well.
 5. The combinationof claim 4 wherein the frequency of said low frequency load inverter isvaried to minimize variations in the power requirements of said electricmotor driving said pump-jack oil well over the operating cycle of saidpump-jack oil well.
 6. The combination of claim 4 wherein the frequencyof said low frequency load inverter is established to match the oilpumping rate of said pump-jack oil well with the rate at which oil seepsinto the oil well.
 7. The combination of claim 2 wherein said repetitiveaxial motion machine driven by an electric motor is a pump-jack oilwell, and said processor varies the instantaneous frequency of said lowfrequency load inverter over the operating cycle of said pump-jack oilwell.
 8. The combination of claim 2 wherein said repetitive axial motionmachine driven by an electric motor is a pump-jack oil well, and saidprocessor varies the instantaneous voltage of said low frequency loadinverter over the operating cycle of said pump-jack oil well.
 9. Thecombination of claim 2 wherein said repetitive axial motion machinedriven by an electric motor is a pump-jack oil well, and said processorvaries the instantaneous current of said low frequency load inverterover the operating cycle of said pump-jack oil well.
 10. The combinationof claim 2 wherein said repetitive anal motion machine driven by anelectric motor is a pump-jack oil well, and said processor varies thefrequency of said low frequency load inverter over the operating cycleof said pump-jack oil well to reduce variations in the powerrequirements of said electric motor driving said pump-jack oil well. 11.The combination of claim 2 wherein said repetitive axial motion machinedriven by an electric motor is a pump-jack oil well, and said processorvaries the voltage or current of said low frequency load inverter overthe operating cycle of said pump-jack oil well to control the slip ofsaid electric motor driving said pump-jack oil well.
 12. The combinationof claim 2 wherein said repetitive axial motion machine driven by anelectric motor is a pump-jack oil well, and, over the operating cycle ofsaid pump-jack oil well, said processor controls the instantaneouspumping work performed by said pump-jack oil well and the instantaneouspumping work being extracted from said pump-jack oil well.
 13. Thecombination of claim 2 wherein said repetitive axial motion machinedriven by an electric motor is a pump-jack oil well, and said processorcases the total of instaneous pumping energy required or produced bysaid pump-jack oil well, and the instantaneous kinetic energy extractedfrom or inserted into said pump-jack oil well, to be substantaillyconstant over the operating cycle of said pump-jack oil well.
 14. Thecombination of claim 3 wherein said repetitive axial motion machinedriven by an electric motor is a pump-jack oil well having axial androtational masses, and said processor varies the frequency of said lowfrequency load inverter to accelerate and decelerate said axial androtational masses of said pump-jack oil well to control the powerrequirements of said electric motor driving said pump-jack oil well. 15.The combination of claim 14 wherein the frequency of said low frequencyload inverter is varied to minimize variations in the power requirementsof said electric motor driving said pump-jack oil well over theoperating cycle of said pump-jack oil well.
 16. The combination of claim14 wherein the frequency of said low frequency load inverter isestablished to match the oil pumping rate of said pump-jack oil wellwith the rate at which oil seeps into the oil well.
 17. The combinationof claim 3 wherein said repetitive axial motion machine driven by anelectric motor is a pump-jack oil well, and said processor varies theinstantaneous frequency of said low frequency load inverter over theoperating cycle of said pump-jack oil well.
 18. The combination of claim3 wherein said repetitive axial motion machine driven by an electricmotor is a pump-jack oil well, and said processor varies theinstantaneous voltage of said low frequency load inverter over theoperating cycle of said pump-jack oil well.
 19. The combination of claim3 wherein said repetitive axial motion machine driven by an electricmotor is a pump-jack oil well, and said processor varies theinstantaneous current of said low frequency load inverter over theoperating cycle of said pump-jack oil well.
 20. The combination of claim3 wherein said repetitive axial motion machine driven by an electricmotor is a pump-jack oil well, and said processor varies the frequencyof said low frequency load inverter over the operating cycle of saidpump-jack oil well to reduce variations in the power requirements ofsaid electric motor driving said pump-jack oil well.
 21. The combinationof claim 3 wherein said repetitive axial motion machine driven by anelectric motor is a pump-jack oil well, and said processor varies thevoltage or current of said low frequency load inverter over theoperating cycle of said pump-jack oil well to control the slip of saidelectric motor driving said pump-jack oil well.
 22. The combination ofclaim 3 wherein said repetitive axial motion machine driven by anelectric motor is a pump-jack oil well, and, over the operating cycle ofsaid pump-jack oil well, said processor controls the instantaneouspumping work performed by said pump-jack oil well and the instantaneouspumping work being extracted from said pump-jack oil well.
 23. Thecombination of claim 3 wherein said repetitive axial motion machinedriven by an electric motor is a pump-jack oil well, and said processorcauses the total of instantaneous pumping energy required or produced bysaid pump-jack oil well, and the instantaneous kinetic energy extractedfrom or inserted into said pump-jack oil well, to be substantiallyconstant over the operating cycle of said pump-jack oil well.
 24. Incombination: a permanent magnet turbogenerator/motor including apermanent magnet generator/motor, a compressor, and a gas turbine havinga combustor; a pump-jack oil well driven by an electric induction motorsupplied with electrical power by said permanent magnetturbogenerator/motor; and a controller operably associated with saidpermanent magnet turbogenerator/motor and said pump-jack oil well toestablish a variable frequency time profile for said electric inductionmotor of said pump-jack oil well which provides a generally constantpower level for said permanent magnet turbogenerator/motor.
 25. Thecombination of claim 24 wherein said controller includes a plurality ofprimary control loops.
 26. The combination of claim 25 wherein one ofsaid primary control loops is a turbine exhaust gas temperature controlloop.
 27. The combination of claim 25 wherein one of said primarycontrol loops is a turbogenerator speed control loop.
 28. Thecombination of claim 25 wherein one of said primary control loops is apower control loop.
 29. The combination of claim 25 wherein said primarycontrol loops include a turbine exhaust gas temperature control loop anda turbogenerator speed control loop.
 30. The combination of claim 25wherein said primary control loops include a turbine exhaust gastemperature control loop and a power control loop.
 31. The combinationof claim 25 wherein said primary control loops include a power controlloop and a turbogenerator speed control loop.
 32. The combination ofclaim 25 wherein said primary control loops include a turbine exhaustgas temperature control loop, a turbogenerator speed control loop, and apower control loop.
 33. The combination of claim 32 wherein said turbineexhaust gas temperature control loop and said turbogenerator speedcontrol loop command fuel input to the turbogenerator combustor.
 34. Thecombination of claim 33 and in addition a selector to select the minimumfuel command from said turbine exhaust gas temperature control loop andsaid turbogenerator speed control loop.
 35. The combination of claim 32wherein said controller additionally includes a turbogenerator speedcommand control loop and a turbogenerator power command control loop.36. The combination of claim 32 wherein said controller additionallyincludes a maximum turbogenerator speed control loop and a maximumturbine exhaust gas temperature control loop.
 37. The combination ofclaim 24 wherein said pump-jack oil well includes a down hole rodstring, and said controller utilizes the phase relationship of thevoltage and current of said electric induction motor to both measure theresonant velocities of the down hole rod string and to damp saidresonances with modulations in the torque of said electric inductionmotor.
 38. The combination of claim 24 wherein said controller includes;a high frequency inverter synchronously connected to said permanentmagnet turbogenerator/motor; a low frequency load inverter operablyconnected to said electric motor driving said repetitive axial motionmachine; a direct current bus electrically connecting said highfrequency inverter with said low frequency load inverter; and aprocessor to control the frequency and voltage/current of said highfrequency inverter and said low frequency load inverter.
 39. Thecombination of claim 38 wherein said processor includes a plurality ofprimary control loops.
 40. The combination of claim 39 wherein one ofsaid primary control loops is a turbine exhaust gas temperature controlloop.
 41. The combination of claim 39 wherein one of said primarycontrol loops is a turbogenerator speed control loop.
 42. Thecombination of claim 39 wherein one of said primary control loops is apower control loop.
 43. The combination of claim 39 wherein said primarycontrol loops include a turbine exhaust gas temperature control loop anda turbogenerator speed control loop.
 44. The combination of claim 39wherein said primary control loops include a turbine exhaust gastemperature control loop and a power control loop.
 45. The combinationof claim 39 wherein said primary control loops include a power controlloop and a turbogenerator speed control loop.
 46. The combination ofclaim 39 wherein said primary control loops include a turbine exhaustgas temperature control loop, a turbogenerator speed control loop, and apower control loop.
 47. The combination of claim 46 wherein said turbineexhaust gas temperature control loop and said turbogenerator speedcontrol loop command fuel output to the turbogenerator combustor. 48.The combination of claim 47 and in addition a selector to select theminimum fuel command from said turbine exhaust gas temperature controlloop and said turbogenerator speed control loop.
 49. The combination ofclaim 46 wherein said controller additionally includes a turbogeneratorspeed command control loop and a turbogenerator power command controlloop.
 50. The combination of claim 46 wherein said controlleradditionally includes a maximum turbogenerator speed control loop and amaximum turbine exhaust gas temperature control loop.
 51. A method ofcontrolling a system including a permanent magnet turbogenerator/motorand a repetitive axial motion machine driven by an electric motor,comprising the steps of: providing electrical power from said permanentmagnet turbogenerator/motor to said electric motor of said repetitiveaxial motion machine; and controlling said permanent magnetturbogenerator/motor and said repetitive axial motion machine toestablish a variable frequency time profile for said electric motor ofsaid repetitive axial motion machine which provides a generally constantpower level for said permanent magnet turbogenerator/motor.